Following the rapid advance of modern electronic technique, more and more multifunctional, high-speed, high-power, miniaturized and compact electronic components and products have been developed. In practice, when operating at high speed, these electronic products at the same time generate high heat. Therefore, it is necessary to use a heat dissipation mechanism to immediately dissipate the heat so as to keep the electronic circuit functioning normally. A fan system is a major part of a heat dissipation mechanism. The fan system serves to create airflow for enhancing heat exchange rate so as to quickly dissipate the heat.
At subscriber end, the number of the fans of the fan system can be increased or decreased in accordance with the requirement of the subscriber end. The controlling unit or controlling chip of the fan system serves to drive the fans and control rotational speed thereof. Accordingly, the rotational speed of the fans can be adjusted in adaptation to the actual operation unit of the subscriber end.
When the fans of the fan system are started, the power supply of the fan system will supply the fans with start current and then operation current to keep the fans operating. The start current is generally more than twice the operation current.
Therefore, in the case that the fan system includes multiple fans, which are to be used at the same time, the power supply will need to supply start current for many fans. However, as foresaid, the start current is generally more than twice the operation current. Therefore, when started at the same time, the voltage of the fan system power supply will be pulled down. In this case, other equipments of the fan system can hardly normal function. Also, after started, the fans will instantly operate at full speed. The start rotational speed is so high as to make great noise. Moreover, in normal full-speed operation of the fan system, failure or so-called “lock” of the fans may happen. In the case of lock of the fans, the temperature of the fan system and the fans will highly rise to cause burnout of the fans.
According to the above, the conventional fan system circuit module has the following defects:    1. When the fans are started at the same time, the voltage of the fan system power supply will be pulled down. In this case, other equipments of the fan system can hardly normal function.    2. After started, the fans will instantly operate at full speed. The start rotational speed is so high as to make great noise.    3. In the case of lock of the fans, the temperature of the fan system will highly rise to cause burnout of the fans.